Exam Questions And Correct Answers

Northwest Territories Wastewater Treatment Operator Level 1 Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary purpose of wastewater

treatment?

• To produce drinking water
• To remove solid waste only
• To protect public health and the environment
• To reduce water temperature

Rationale: The primary purpose of wastewater treatment is to remove

pollutants and pathogens from wastewater to protect public health and the environment. 1 / 4

• What does BOD stand for in wastewater treatment?
• Biological Oxygen Demand
• Biochemical Oxygen Duration
• Biochemical Oxygen Demand
• Biological Oxidation Duration

Rationale: BOD measures the amount of oxygen required by

microorganisms to decompose organic matter in water.

• Which stage of wastewater treatment primarily removes solids?
• Secondary treatment
• Primary treatment
• Tertiary treatment
• Disinfection

Rationale: Primary treatment uses physical processes such as screening

and sedimentation to remove settleable solids.

• What is the main purpose of secondary treatment?
• Chemical precipitation
• Biological treatment to remove dissolved organic matter
• Disinfection
• Screening

Rationale: Secondary treatment uses biological processes, often activated

sludge or biofilm systems, to degrade organic matter. 2 / 4

• Which of the following is considered a pathogen commonly found in

wastewater?

• Sand
• Nitrogen
• E. coli
• Phosphate

Rationale: E. coli is a bacteria used as an indicator of pathogenic

contamination in wastewater.

• What is the primary function of a grit chamber?
• Remove oil and grease
• Remove dissolved chemicals
• Remove sand, gravel, and heavy solids
• Aerate the wastewater

Rationale: Grit chambers remove heavy inorganic solids like sand and

gravel to prevent damage to downstream equipment.

• Which of the following is the typical pH range for municipal

wastewater?

A. 2–4

B. 5–6

C. 6–9

D. 10–12 3 / 4

Rationale: Municipal wastewater is usually slightly acidic to slightly

alkaline, typically between 6 and 9.

8. Sludge age in an activated sludge system refers to:

• The time sludge spends in the inlet
• The time sludge spends in the clarifier
• The average time microorganisms remain in the system
• The storage time before disposal

Rationale: Sludge age (mean cell residence time) is the average time the

biomass remains in the system, influencing biological activity.

• What is the main purpose of disinfection in wastewater treatment?
• Remove suspended solids
• Destroy pathogenic microorganisms
• Reduce BOD
• Remove nutrients

Rationale: Disinfection, often by chlorine or UV, eliminates harmful

pathogens before discharge.

• Which chemical is commonly used for disinfection?
• Sodium hydroxide
• Sulfuric acid
• Chlorine
• Ammonia
• / 4